The present invention relates to a thermal printer, and more specifically, to a thermal printer that is able to efficiently clean a thermal head and create a conversion table for recording density correction.
A thermal image recording is utilized for recording of an ultrasonic diagnosis image, which is performed by using thermal (heat sensitive) recording material having a thermal recording layer formed on a supporting body such as a paper and a film. Moreover, since the thermal image recording has advantages that wet development is not necessary and that handling is easy, a range of its utilization has spread in the recent years in the image recording of medical diagnosis not only in a small image recording such as the ultrasonic diagnosis but also in applications where an image is required to be large in size and high in quality such as MRI (magnetic resonance imaging) diagnosis, X-ray diagnosis and the like.
As widely known, in the thermal image recording, a thermal head having a glaze where exothermic elements equivalent in number to the number of pixels in one line being arrayed in one direction is used. In the state where the glaze is pressed a little against the thermal recording layer of the thermal recording material, each exothermic element of the glaze is heated in accordance with image data of a recorded image while the thermal head and the thermal recording layer are relatively moved in a direction perpendicular to the array direction of the above-described exothermic elements. Thus, the thermal recording layer of the thermal recording material is heated to record the image.
Moreover, in the thermal printer, various processing for management, adjustment and maintenance are performed other than the actual image recording. Various kinds of materials are prepared in advance for the processing for management, adjustment and maintenance depending on applications thereof.
For example, when being recorded by pressing a heated thermal head against the thermal recording material, the image is recorded on the surface of the thermal recording material while the recording substance and lubricating substance of the thermal recording layer melt. Therefore, a stain and melted matter such as lubricant tend to be accumulated on the surface of the thermal head. There exists a problem that a recorded image becomes uneven if the melted matter builds up so much that it enters between the thermal recording material and the thermal head.
On the other hand, the melted matter adhered to the surface of the thermal head is gradually fixed on the surface due to continuous heating by the thermal head, and in some cases, the melted matter becomes so rigidly fixed that a cleaning solution cannot remove it easily. In such a case where removal of a fixed matter by the cleaning processing is difficult, the only solution has been to scrape off the fixed matter on the surface of the thermal head by using, for example, a lapping film having a strong abrasive power.
The above-described lapping film is the one in which abrasive agent such as alumina grains is adhered on the surface of the film as a supporting body, and by outputting the lapping film instead of the foregoing thermal recording material, the fixed matter on the surface of the thermal head can be scraped off. However, since the lapping film has such a strong abrasive power that it scrapes off even ceramic which is a protective coat of the thermal head, there exists a problem that wear of the thermal head becomes hastened and the life thereof becomes shortened.
Also, the lapping film has an advantage that it can remove a stubborn stain and fixed matter, but at the same time, has a drawback that it generates very large sound (noise) during operation. Therefore, there exists another problem that the lapping film is inappropriate for use in a hospital and the like. The assignee previously proposed an effective solution for the above-described various problems in Japanese Patent Application No. Hei8 (1996)-108944 xe2x80x9cThermal image recording apparatusxe2x80x9d (refer to Japanese Patent Laid-Open No. Hei9 (1997)-295420 gazette).
In this solution, every time a specified number of the recorded images are formed, energy is not applied to the thermal head or energy lower than a predetermined value is applied thereto, and the thermal recording material is output to a thermal image recording apparatus. Thus, the thermal image recording apparatus is allowed to have a cleaning mode for cleaning the thermal head. Specifically, the thermal recording material is used instead of the foregoing lapping film in the state where the thermal head is not heated.
Also on the other hand, the thermal recording material is as well used in density correction which prevents fluctuation of an image density upon recording the image on the thermal recording material by driving the thermal head in accordance with an image signal. For example, a technology disclosed in Japanese Patent Application No. Hei2 (1990)-272924 xe2x80x9cMethod of density correction in image recordingxe2x80x9d (refer to Japanese Patent Laid-Open No. Hei4 (1992)-147870 gazette) applied by the assignee can be cited.
This method is a density correction method that is performed as follows. A plurality of density patterns are recorded on one piece of the thermal recording material at a front portion of with respect to a passage direction of the thermal head, before the image is recorded, and the density of each of the above-described density patterns is measured prior to the image recording on the thermal recording material. Based on the measurement result, a conversion table is created for performing a conversion processing of the image signal to be recorded on the thermal recording material. The above-described image signal is then subjected to the conversion processing by the conversion table when recording the above-described image on the thermal recording material on which the density patterns utilized for creating the conversion table are recorded.
In the above-described density correction method in the image recording, a plurality of density patterns (a kind of test patterns) for obtaining density data, which serves as a base for the density correction, are recorded on one piece of the thermal recording material prior to the actual image. The density of the recorded patterns is measured, and the conversion table for the density correction is created from a signal of the above-described density patters (a reference value for obtaining a predetermined density) and a density signal based on the density actually recorded.
As described above, in the thermal printer, various kinds of materials have been prepared in advance for processing for management, adjustment and maintenance, depending on applications thereof. However, there exists a problem that extra cost for maintenance and management is necessary other than the cost of the material itself in order to prepare in advance the various kinds of materials depending on each application.
The present invention has been created in consideration of the foregoing circumstances. The object of the present invention is to solve the problems in the prior art and to provide a thermal printer in which various kinds of materials used for management, adjustment and maintenance can be utilized more efficiently than before.
In order to attain the object described above, the present invention provides a thermal printer for forming a recorded image in accordance with image data on a thermal recording material by using a thermal head, comprising: a first control mode for cleaning the thermal printer by using the thermal recording material; and a second control mode for measuring density of the thermal printer by using the thermal recording material, wherein the first and second control modes are switched at a partway of one piece of the thermal recording material.
Preferably, the first control mode uses the thermal recording material without heating the thermal head at all.
Preferably, the second control mode allows the thermal head to perform heating for generating predetermined test patterns, density of which vary in a plurality of steps.
Preferably, the switching of the first and second control modes at a partway of one piece of the thermal recording material is performed from the second control mode to the first control mode.
Preferably, the switching of the first and second control modes at a partway of one piece of the thermal recording material is performed from the first control mode to the second control mode.